NOAA scientist's team says the thermometers have it right

The thermometers aren't going haywire. The planet, itself, is recording the same reality. The Earth is warming, and doing so at a quickening pace.

A new compilation of temperature records derived from geological samples such as ice cores, lake sediment layers and coral growth shows the same warming trends from 1880 to 1995 that are reflected by thermometer readings over that time.

The study, titled "Global Warming in an Independent Record of the Past 130 Years," was published recently online in Geophysical Research Letters; its lead author is David Anderson, the head of the paleoclimatology branch at the National Oceanic and Atmospheric Administration's National Climatic Data Center in Boulder.

Researchers from the University of Colorado, the University of Bern in Switzerland and the University of South Carolina also contributed to the study.

"It's like getting a second opinion from a doctor," Anderson said Friday. "There has been some controversy about whether the thermometer-based record of last 100 years has so many problems, that maybe it's not warming. There've been scientists testifying on the Senate floor as to whether the planet is really warming or not.

"We've been looking around the world and seeing the glaciers receding... but this is the mathematical or statistical backup of that very obvious change. It's independent evidence that over the last 120 years, there's a significant warming trend, just like the thermometer shows."

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But the record reflected by thermometer readings is incomplete. Until more recent history, there was no shortage of thermometers in settled urban centers, but none, for example, in the Arctic Circle, Antarctica or the remote jungles of South America.

In an alternative approach to taking the Earth's historical temperatures, researchers analyzed "proxies" such as ice cores, the shells of marine plankton and coral growth layers; as an example, plankton shells and coral skeletons record temperature changes in their ratio of oxygen isotopes.

Through this analysis, which used 173 independent proxy datasets to draw a record from 1730 to 1995, scientists have succeeded in compiling temperature records that confirm what available thermometer records also show.

As an example, a warm stretch in the 1940s that was recorded in the global surface temperature record is mirrored by the paleoclimate record. And both records indicate that the global warming for the last 15 years of the study period, 1980 to 1995, is markedly faster -- 65 percent greater -- over the long-term warming trend spanning 1880 to 1995.

"Not only is there a warming trend, but it is geographically widespread," Anderson said. "It is found in Antarctica, it is found in the Arctic and it is found in the tropical oceans."

The temperatures reflected in the paleo-proxies, in Anderson's opinion, are not currently sufficiently accurate to calibrate them to variables of tenths-of-a-degree one direction or another; he expects that later studies by his team and others will improve the accuracy of the paleo-proxies.

"The correlation of this paleoclimate dataset with the global surface temperature record has important implications in climate science and provides evidence of the significance of paleoclimate research," said Thomas Karl, director of the National Climatic Data Center, in a news release. "Temperature reconstructions, like this one, continue to play a significant role in understanding the global climate by quantitatively extending the record back in time in an independent, objective way."